Solve for $k$ : $23 = 18 + k$
Answer: Subtract $18$ from both sides: $ \begin{eqnarray} \\ \hphantom{23 {- 18}} &\hphantom{=}& \hphantom{k} \\ 23 &=& 18 + k \\ \\ {-18} && {-18} \\ \end{eqnarray} $ $ \begin{eqnarray} \\ 23 {- 18} &=& k \\ \end{eqnarray} $ Simplify. $ k = 5$